A drive unit suspension of relevant type is disclosed in pending U.S. patent application Ser. No. 771,812, filed Sept. 3, 1985 and assigned to the assignee of this invention.
In this drive unit suspension, the cross-section of the member for insertion into the opening and the opening are of trapezoid configuration, so that relative movement between that member and the elastomeric portion is not possible. Another reason that such relative movement is precluded is that the trapezoid-shaped member is cemented to the elastomeric portion.
In another drive unit suspension, that is in common use, the bracket is connected to the elastomeric portion by means of two threaded bolts that are arranged one above the other. In this arrangement, too, any movement of the bracket causes movement in the elastomeric portion so that the desired damping and isolation will occur.
Since the area where the member and the elastomeric portion are joined is never perfectly even, the acoustic connection between the bracket and the damping block will, of necessity, be acoustically imperfect. In order to raise the acoustic comfort to a satisfactory level, some additional procedures are normally required. The usual procedure is to bridge the U-shaped cross-section of the bracket by a sheet metal member. This sheet metal member is welded to the bracket and serves as a means to provide acoustic reinforcement and stabilization. However, this subsequent procedure is cost-intensive and is not very effective. The latter fix also introduces the potential for errors or inaccuracies.
Apart from these shortcomings, experience under practical operating conditions has been that during periods of acceleration, the elastomeric portion will be, due to the tilting movement of the drive unit, subjected to excessive twisting. As a result, the elastomeric portion may harden and assume a different spring characteristic. This means that its ability to dampen drive unit vibrations is substantially impaired.